One vertex per element, one color per generator, with an edge from x to x·s.
(5,6)(7,8)(9,11)(10,12)(13,14,17,19)(15,24,25,28)(16,23,18,22)(20,27,21,26)(1,2)(3,4)(5,7)(6,10)(8,11)(9,12)(14,19)(15,25)(22,23)(26,27) involution — undirected(2,4)(5,8,9,10)(6,7,11,12)(13,15)(14,20)(16,26)(17,25)(18,27)(19,21)(22,24)(23,28)(6,11)(7,12)(13,15)(14,21)(16,26)(17,25)(18,27)(19,20)(22,28)(23,24) involution — undirected(13,16,17,18)(14,22,19,23)(15,26,25,27)(20,24,21,28)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.